In a large skillet, combine blueberries, grapes, sugar, ginger, rosemary, and vinegar. Bring to a boil; reduce heat, and simmer gently until grapes begin to break down, 15 to 20 minutesAdvertisement
Season with 1/4 teaspoon salt and 1/4 teaspoon pepper. Let cool completely before using or storing.
Relish can be refrigerated, covered, up to 2 weeks.